A common process step in the production of many snack foods is the introduction of a plurality of individual "bite size" pieces of uncooked or partially cooked food material into a container of hot oil for frying. As the food pieces are introduced into the hot oil, it is generally desirable to disperse the pieces within the oil to provide for efficient utilization of the body of hot oil and to prevent the pieces sticking to each other. After the initial dispersal of the pieces in the hot oil, it is desirable that the pieces be further agitated so that the pieces do not stick to each other and so that they cook more uniformly. When the material is a snack food in hot oil, the pieces will generally not cook properly unless all surfaces are periodically submerged or turned "face-down" into the oil. Previously, this was generally accomplished using manual agitation of the pieces in the oil, for example, by an operator using a device such as a stainless steel rake shaped similar to an ordinary leaf rake.
Batch processing of food items is characterized by a temperature cycle which affects the quality and uniformity of the food product. The temperature cycle for the production of potato chips is representative of batch processing of food items. One of the problems with the prior manual agitation method is that the temperature cycle could not be controlled as well as desired. In a typical process a burner is utilized to apply a heat input to the oil. When the processing liquid, typically a cooking oil, reaches a predefined temperature, the food material, such as raw potato slices, is added to the cooking oil. Upon the addition of the potato slices to the cooking oil, the oil temperature drops as the water in the potato slices is boiled off. As the cycle continues, the rate of water removal from the potato slices decreases, the oil temperature ceases to fall and begins to rise again. At a predetermined point in the cycle, or when the oil temperature reaches a predetermined value, the batch process is completed, the chips having been cooked the proper amount. The chips are then removed from the hot oil and a new batch cycle can be started. However, as the chips are removed at the end of a cycle, the oil temperature rises. If the amount of time taken to remove the cooked chips and to prepare for a new cycle is not precisely uniform, the starting temperature of each batch may not be uniform. A nonuniform start temperature can lead to nonuniform product. Severe variations in start temperature can lead to unusable product. In the extreme case, if the operator is not prepared to start the batch at the right point, the oil temperature can exceed a predetermined value and the system will automatically shut off for safety reasons. In this event, a batch of material must be run to reduce the oil temperature and that batch of material will not be usable.
The manual method of raking the food items is unsatisfactory for several reasons. First, it leads to less uniform product because the operator is unable to stir or agitate the objects as repeatably as a mechanical device. Second, the operator is responsible for monitoring the process temperature as well as agitating the pieces. The operator may not uniformly stir the batch while monitoring the temperature. Third, the product may be wasted by being flung out of the batch by excessive manual agitation. Fourth, some snack foods, such as potato chips, produce a water vapor cloud over the oil as water is removed from the raw or partially cooked potato slices. The cloud of water vapor makes it difficult for the operator to see the slices, which hinders the operator's ability to uniformly agitate the batch. Last, the cloud of water vapor is hot and unpleasant for the operator to work in, making it more difficult to uniformly perform the job early in the batch process cycle.
A recently offered automatic device uses a drum and metal paddles for agitation and an air blast for dispersal. This device is essentially an automated version of an operator with a rake. It succeeds in reducing manpower but is mechanically complex. The drum and paddle system is subject to fouling with the food material and is difficult to keep clean. Its mechanical complexity potentially creates new maintenance problems.
Therefore, a need exists for a simplified automated kettle rake which reduces the need for manual labor. Such a device must be capable of circulating raw or uncooked food material which either floats on the surface or sinks to the bottom of the container filled with a liquid. The device must also be capable of circulating and dispersing the food pieces. Moreover, such a device should be able to automatically remove the food pieces after they have been cooked.